[zeroeight]

Quote:

hmm wait I thought that statement meant 1-5 is very close in sound quality, while six and above ( to 30 ) has jumps in sound quality?

I read it that way as well.  What confused me was the overlap between the 5 and 6.  So 5-30 were very close while 1-6 were much great variance.

 

[grokit]

I read about damping some time ago but forgot what it was.
 
Here we go, clear as mud (sigh):

The damping circuit

The voltage generated by the moving voice coil forces current through three resistances:

1. the resistance of the voice coil itself;
2. the resistance of the interconnecting cable; and
3. the output resistance of the amplifier.

 

"A high damping factor indicates that an amplifier will have greater control over the movement of the speaker cone, particularly in the bass region near the resonant frequency of the driver's mechanical resonance. However, the damping factor at any particular frequency will vary, since driver voice coils are complex impedances whose values vary with frequency. In addition, the electrical characteristics of every voice coil will change with temperature; high power levels will increase coil temperature, and thus resistance. And finally, passive crossovers (made of relatively large inductors, capacitors, and resistors) are between the amplifier and speaker drivers and also affect the damping factor, again in a way that varies with frequency.

 

Modern solid state amplifiers, which use relatively high levels of negative feedback to control distortion, have extremely low output impedances—one of the many consequences of using feedback—and small changes in an already low value change overall damping factor by only a small, and therefore negligible, amount.

Thus, high damping factor values do not, by themselves, say very much about the quality of a system; most modern amplifiers have them, but vary in quality nonetheless... Tube amplifiers typically have much lower feedback ratios, and in any case almost always have output transformers that limit how low the output impedance can be. Their lower damping factors are one of the reasons many audiophiles prefer tube amplifiers. Taken even further, some tube amplifiers are designed to have no negative feedback at all."

 

To me the parts I bolded seem to contradict each other, where a high damping factor offers greater control of the cone, but audiophiles prefer a low damping factor?

In my simpleton understanding of this, it's basically a way of varying resistance to manufacture, or tune, a given frequency response... and it has something to do with impedance 

 

[Wedge]

You know most places I go, Analog and Microwave Design are considered to Black Magic!  

 
Quote:

Originally Posted by kwkarth /img/forum/go_quote.gif

Magic!  

 

 

 

[kwkarth]

Quote:

I read about damping some time ago but forgot what it was.
 
Here we go, clear as mud (sigh):

The damping circuit

The voltage generated by the moving voice coil forces current through three resistances:

1. the resistance of the voice coil itself;
2. the resistance of the interconnecting cable; and
3. the output resistance of the amplifier.

 

"A high damping factor indicates that an amplifier will have greater control over the movement of the speaker cone, particularly in the bass region near the resonant frequency of the driver's mechanical resonance. However, the damping factor at any particular frequency will vary, since driver voice coils are complex impedances whose values vary with frequency. In addition, the electrical characteristics of every voice coil will change with temperature; high power levels will increase coil temperature, and thus resistance. And finally, passive crossovers (made of relatively large inductors, capacitors, and resistors) are between the amplifier and speaker drivers and also affect the damping factor, again in a way that varies with frequency.

 

Modern solid state amplifiers, which use relatively high levels of negative feedback to control distortion, have extremely low output impedances—one of the many consequences of using feedback—and small changes in an already low value change overall damping factor by only a small, and therefore negligible, amount.

Thus, high damping factor values do not, by themselves, say very much about the quality of a system; most modern amplifiers have them, but vary in quality nonetheless... Tube amplifiers typically have much lower feedback ratios, and in any case almost always have output transformers that limit how low the output impedance can be. Their lower damping factors are one of the reasons many audiophiles prefer tube amplifiers. Taken even further, some tube amplifiers are designed to have no negative feedback at all."

 

To me the parts I bolded seem to contradict each other, where a high damping factor offers greater control of the cone, but audiophiles prefer a low damping factor?

In my simpleton understanding of this, it's basically a way of varying resistance to manufacture, or tune, a given frequency response... and it has something to do with impedance 

I can see why this is confusing to people.  Not sure where you got that bit of information, but there are some dated inaccuracies contained in it that add to the confusion.  The first bolded statement is generally true, but the second bolded statement is not at all necessarily true.  The second statement is apparently some sort of conclusion the writer jumped to without stating how they arrived there.  
 
The author appears to be concluding that output transformer secondary windings are solely responsible for the "sound" of all tube based speaker amplifiers.  This conclusion is not necessarily true at all.  IF an amp is transformer coupled at the output, the transformer is probably responsible for some of the sonic character and performance of the amp, but certainly not all.  
 
The last sentence proffered by the author mentions some tube amps being designed with no negative feedback.  Today, we have a number of completely solid state amps designed employing zero global feedback as well.  
 
Damping factors are not how manufacturers "tune" or "voice" an amplifier.  Negative feedback is used primarily as a means to lessen non linearities, both intra stage and inter stage in an amp.  High negative feedback became a very popular way to manage gain factors as well as non linearities in op-amp based amplifiers.  
 
Along with the good there is also the bad that goes along with almost any design methodology.  The trade offs must be weighed.
 
 

 

[kwkarth]

One of the best (to me) illustrations of the effectiveness of electromagnetic damping comes by way of an electric drill motor.
 
Consider the average variable speed cordless drill...  When one pulls the trigger all the way back so the drill runs at its highest speed, and then releases the trigger, the drill stops rotating instantly.  Why?  Try this experiment:
 
While the trigger is fully depressed and the drill is running along at full speed, unplug the battery pack from the handle while keeping the trigger fully depressed.  What happens?  Try it, and tell me what you observe.  Then we can talk about what happened.

 

[Armaegis]

If only I had a cordless drill...

 

[Mr Do]

I hope we see some more love for the Sound Quest SQ-84 II tube amp around here.  Otherwise, nice read as always.
 
Thanks,
Mr. Do!
 

 

[grokit]

I tried it, the drill continues to rotate on it's own momentum, meaning it needs to have power to provide the resistance--negative feedback?--to come to a faster stop.

 

[kwkarth]

Quote:

I tried it, the drill continues to rotate on it's own momentum, meaning it needs to have power to provide the resistance--negative feedback?--to come to a faster stop.

Now, do the same test and let the trigger go.  The drill stops rotating instantly right?  What happened?  The inputs to the motor are shorted, which is like an infinitely high damping factor in an amplifier.  As the drill motor rotates, it generates its own "back emf,"  With its "input" shorted, that back emf electromagnetically countermands the rotation of the motor.  Electronic braking works the same way in any hybrid automobile.  The battery in the vehicle becomes the load on the motor instead of driving force and the motor charges the battery with the energy shunted into it.
 

 

[grokit]

 
Quote:

Now, do the same test and let the trigger go.  The drill stops rotating instantly right?  What happened?  The inputs to the motor are shorted, which is like an infinitely high damping factor in an amplifier.  As the drill motor rotates, it generates its own "back emf,"  With its "input" shorted, that back emf electromagnetically countermands the rotation of the motor.  Electronic braking works the same way in any hybrid automobile.  The battery in the vehicle becomes the load on the motor instead of driving force and the motor charges the battery with the energy shunted into it.

I would love to hear you expand on the first part that I bolded. But the second part, isn't the inverse true? It seems that electricity is creating the braking action on the drill, but the braking action on a hybrid is creating the electricity.
 

 

[kwkarth]

Quote:

 

I would love to hear you expand on the first part that I bolded. But the second part, isn't the inverse true? It seems that electricity is creating the braking action on the drill, but the braking action on a hybrid is creating the electricity.
 

Whether a speaker or a drill motor, they both work both ways by Maxwell's equations/principles.  When a coil of wire is moved through magnetic lines of force from the permanent magnet, current flows in a closed circuit.  Conversely, when current is passed through a coil of wire while it is immersed in a magnetic field, the magnetic field which is generated by the current flowing in the wire, pushes against the permanent magnetic field and moves the voice coil or drill motor rotor, as the case may be.
 
In the case of the drill motor, when the trigger is released, it shorts the input to the motor.  The back emf generated in the motor's windings stops it instantly.
 
 

 

[zorin]

Skylab,  any experience with  HeadCode, ValveCode and PortaCode amps from Triad Audio ?

 

[Skylab]

I am supposed to receive one of the very first of the new Valvecodes for review.

 

[florestan]

 
Quote:

I am supposed to receive one of the very first of the new Valvecodes for review.

 
Any idea when that might happen? I love the Lisa III and am very curious to see what Triad would make on a larger scale (particularly with tubes).
 
As for my little experiment, using the Zvex breakout box with my 300b speaker amp, it works REALLY well! I initially plugged my LCD's in, the volume set to 0, with some trepidation. I used my newly acquired Stealth as the pre-amp (which arrived on Saturday) and the first 2 jacks were very quiet, the first dead silent in fact. The 3rd however introduces quite a bit of hum; too much to be of any use with either the LCD-2 or AKG K701; and, the HD650's are so sensitive that I wouldn't want to use anything but the first jack to power them. Still, the first jack, with all three headphones is quiet, and very responsive. First impression: "wow, why didn't i do this like 3 years ago." That said, I haven't had time to really compare it in detail to my other headphone set-ups: I spent most of the weekend trying everything I could think of with the Stealth as both a headphone amp and speaker PreAmp. I have to say that I am really quite impressed with it as a Speaker PreAmp, but particularly impressed with how well it matches up with the HD650's. As I was listening I kept thinking that I would be perfectly happy with just this amp and headphone set-up alone . . . what a perfect combination! I feel so fortunate to have picked it up for only $1500 shipped (a steal!).
 
Alternately, when I switched to my Deju Vu Pre, I was reminded just how much higher the noise floor was. Suddenly the 1st jack became the only reasonable option, regardless of headphone (and the Senns were no longer a possible match as they had been with the stealth as a Pre). The Gain is just set too high too listen without a loud and ever present hum. That said, the 1st jack managed to power the LCD-2's cleanly and without any issues. Over the next few weeks I plan to spend allot of time dissecting the different possibilities and comparing the various components to try to understand something more about their individual characteristics and how they might potentially compliment one another in different arrangements. But, for anyone with an efficient (read "quiet") speaker PreAmp/Amp combination and a desire to hear them drive your headphones (particularly the less efficient ones), I would say that the Zvex BreakOut Box is an incredible bargain at $100 and works quite nicely; but, it will take some time and convincing before I consider using it as a full time replacement for my go to options.
 

 

[dallan]

Quote:

I am supposed to receive one of the very first of the new Valvecodes for review.

I am very interested on your thoughts with that as well.